The objective of this proposed research is to determine if there is altered membrane structure in myeloid cells from patients with myeloid or lymphoid leukemias and if altered membrane structure affects phagocytic function of these cells. In order to answer those questions we must: 1) quantitate cell surface receptors on normal blood neutrophils; 2) assess when these receptors develop in normal marrow myeloid precursors; and 3) determine how the presence of these receptors relates to functional capacity. The same studies will then be applied to blood and marrow myeloid cells from patients with myeloid leukemias to determine whether membrane development in terms of quantity and quality of cell surface receptors differs from normal and whether the myeloid leukemias can be classified by these membrane properties. Blood neutrophils from other leukemic patients will be examined to assess whether their membrane differentiation differs from normal membrane differentiation and whether the increased susceptibility to bacterial and fungal infections in these patients is related to abnormal membrane structure and function.